Privoxy is certainly a good choice,
especially for those who want more control and security. Those with the
willingness to read the documentation and the ability to fine-tune
their installation will benefit the most.

One of Privoxy's strengths is that
it is highly configurable giving you the ability to completely
personalize your installation. Being familiar with, or at least having
an interest in learning about HTTP and other
networking protocols, HTML, and "Regular Expressions" will be a
big plus and will help you get the most out of Privoxy. A new installation just includes a very
basic configuration. The user should take this as a starting point
only, and enhance it as he or she sees fit. In fact, the user is
encouraged, and expected to, fine-tune the configuration.

Much of Privoxy's configuration can
be done with a Web browser. But there are areas where configuration
is done using a text editor to edit configuration files. Also note
that the web-based action editor doesn't use authentication and should
only be enabled in environments where all clients with access to
Privoxy listening port can be
trusted.

A web proxy is a service, based on a software such as
Privoxy, that clients (i.e. browsers)
can use instead of connecting to web servers directly. The clients then
ask the proxy to request objects (web pages, images, movies etc) on
their behalf and to forward the data to the clients. It is a
"go-between". For details, see Wikipedia's
proxy definition.

There are many reasons to use web proxies, such as security
(firewalling), efficiency (caching) and others, and there are any
number of proxies to accommodate those needs.

Privoxy is a proxy that is
primarily focused on privacy enhancement, ad and junk elimination and
freeing the user from restrictions placed on his activities. Sitting
between your browser(s) and the Internet, it is in a perfect position
to filter outbound personal information that your browser is leaking,
as well as inbound junk. It uses a variety of techniques to do this,
all of which are under your complete control via the various
configuration files and options. Being a proxy also makes it easier to
share configurations among multiple browsers and/or users.

A long time ago, there was the Internet
Junkbuster, by Anonymous Coders and Junkbusters Corporation.
This saved many users a lot of pain in the early days of web
advertising and user tracking.

But the web, its protocols and standards, and with it, the
techniques for forcing ads on users, give up autonomy over their
browsing, and for tracking them, keeps evolving. Unfortunately, the
Internet Junkbuster did not. Version
2.0.2, published in 1998, was the last official release, available from
Junkbusters Corporation. Fortunately, it had been released under the
GNU GPL, which allowed further development by others.

So Stefan Waldherr started maintaining an improved version of the
software, to which eventually a number of people contributed patches.
It could already replace banners with a transparent image, and had a
first version of pop-up killing, but it was still very closely based on
the original, with all its limitations, such as the lack of HTTP/1.1
support, flexible per-site configuration, or content modification. The
last release from this effort was version 2.0.2-10, published in
2000.

Then, some developers picked up the thread, and started turning the
software inside out, upside down, and then reassembled it, adding many
new features along the way.

The result of this is Privoxy,
whose first stable version, 3.0, was released August, 2002.

As of 2012 the Junkbusters Corporation's website
(http://www.junkbusters.com/) has been shut down, but Privoxy is still
actively maintained.

Though outdated, Junkbusters Corporation continued to offer their
original version of the Internet
Junkbuster for a while, so publishing our Junkbuster-derived software under the same name
would have led to confusion.

There were also potential legal reasons not to use the Junkbuster name, as it was (and maybe still is) a
registered trademark of Junkbusters Corporation. There were, however,
no objections from Junkbusters Corporation to the Privoxy project itself, and they, in fact, shared
our ideals and goals.

The Privoxy developers also believed that there were so many
improvements over the original code, that it was time to make a clean
break from the past and make a name in their own right.

Privoxy is the "Privacy Enhancing
Proxy". Also, its content modification and junk
suppression gives you, the user, more control, more freedom, and
allows you to browse your personal and "private
edition" of the web.

Privoxy picks up where Junkbuster left off. Privoxy still blocks ads and banners, still
manages cookies, and still helps protect your privacy. But, most of
these features have been enhanced, and many new ones have been added,
all in the same vein.

Privoxy's new features include:

Supports "Connection: keep-alive". Outgoing connections can be
kept alive independently from the client.

Supports IPv6, provided the operating system does so too, and
the configure script detects it.

Supports tagging which allows to change the behaviour based on
client and server headers.

Can be run as an "intercepting" proxy, which obviates the need
to configure browsers individually.

Sophisticated actions and filters for manipulating both server
and client headers.

First, there are certain patterns in the locations (URLs) of banner
images. This applies to both the path (you wouldn't guess how many web
sites serve their banners from a directory called "banners"!) and the host (blocking the big banner
hosting services like doublecklick.net already helps a lot).
Privoxy takes advantage of this fact
by using URL patterns to sort out and block the requests for things
that sound like they would be ads or banners.

Second, banners tend to come in certain sizes. But you can't tell the
size of an image by its URL without downloading it, and if you do, it's
too late to save bandwidth. Therefore, Privoxy also inspects the HTML sources of web
pages while they are loaded, and replaces references to images with
standard banner sizes by dummy references, so that your browser doesn't
request them anymore in the first place.

Both of this involves a certain amount of guesswork and is, of
course, freely and readily configurable.

Actually, it's a black art ;-) And yes, it is always possible to
have a broad rule accidentally block or change something by mistake.
You will almost surely run into such situations at some point. It is
tricky writing rules to cover every conceivable possibility, and not
occasionally get false positives.

But this should not be a big concern since the Privoxy configuration is very flexible, and
includes tools to help identify these types of situations so they can
be addressed as needed, allowing you to customize your installation.
(See the Troubleshooting section
below.)

That depends on your expectations. The default installation should
give you a good starting point, and block most ads and unwanted
content, but many of the more advanced features are off by default, and
require you to activate them.

And you will certainly run into situations where there are false
positives, or ads not being blocked that you may not want to see. In
these cases, you would certainly benefit by customizing Privoxy's configuration to more closely match your
individual situation. And we encourage you to do this. This is where
the real power of Privoxy lies!

Modern browsers do indeed have some of the same functionality as Privoxy. Maybe this is adequate for you. But
Privoxy is very versatile and
powerful, and can probably do a number of things your browser just
can't.

In addition, a proxy is good choice if you use multiple browsers, or
have a LAN with multiple computers since Privoxy can run as a server application. This way
all the configuration is in one place, and you don't have to maintain a
similar configuration for possibly many browsers or users.

Note, however, that it's recommended to leverage both your browser's
and Privoxy's privacy enhancing
features at the same time. While your browser probably lacks some
features Privoxy offers, it should
also be able to do some things more reliably, for example restricting
and suppressing JavaScript.

The most important reason is because you have access to everything, and you can
control everything. You can check every line of every configuration
file yourself. You can check every last bit of source code should you
desire. And even if you can't read code, there should be some comfort
in knowing that other people can, and do read it. You can build the
software from scratch, if you want, so that you know the executable is
clean, and that it is yours. In fact, we encourage this level of
scrutiny. It is one reason we use Privoxy ourselves.

Privoxy is free software and
licensed under the GNU General Public License (GPL) version 2. It is free to
use, copy, modify or distribute as you wish under the terms of this
license. Please see the Copyright section
for more information on the license and copyright. Or the LICENSE file that should be included.

There is no
warranty of any kind, expressed, implied or otherwise. That
is something that would cost real money ;-) There is no registration
either.

No, at least not reliably enough to trust it. Privoxy is not designed to be a malware removal
tool and the default configuration doesn't even try to filter out any
malware.

Privoxy could help prevent contact
from (known) sites that use such tactics with appropriate configuration
rules, and thus could conceivably prevent contamination from such
sites. However, keeping such a configuration up to date would require a
lot of time and effort that would be better spend on keeping your
software itself up to date so it doesn't have known
vulnerabilities.

Privoxy should work fine with other
proxies and other software in general.

But it is probably not necessary to use Privoxy in conjunction with other ad-blocking
products, and this could conceivably cause undesirable results. It
might be better to choose one software or the other and work a little
to tweak its configuration to your liking.

Well, we always need help. There is something for
everybody who wants to help us. We welcome new developers, packagers,
testers, documentation writers or really anyone with a desire to help
in any way. You DO
NOT need to be a "programmer".
There are many other tasks available. In fact, the programmers often
can't spend as much time programming because of some of the other,
more mundane things that need to be done, like checking the Tracker
feedback sections or responding to user questions on the mailing
lists.

So first thing, subscribe to the Privoxy Users or the Privoxy Developers mailing list, join the
discussion, help out other users, provide general feedback or report
problems you noticed.

Donations are welcome. Our TODO list is rather long and being able to pay one
(or more) developers to work on Privoxy would make a huge difference,
even if it was only for a couple of weeks. Donations may also be used
for Privoxy-related travel expenses (for example to attend
conferences), for hardware used for Privoxy development and for
hosting expenses etc.

Donations made through Zwiebelfreunde e.V. are tax-deductible in
Germany and other countries that recognize German charitable clubs.
Feel free to use the Subject field to provide a name to be credited
and a list of TODO list items you are interested in the most. For
example: Max Mustermann: #16, #1, #14.

If you have any questions regarding donations please mail to
either the public user mailing list or, if it's a private matter, to
Fabian Keil
(Privoxy's SPI liason) directly.